On this day the first Dhamma Sangayana (Council) is commemorated. It was held three months after the passing away of the Buddha at Rajagahanuvara. Buddha’s chief Attendant, ‘Dhamma Bhandagarika’ Ananda Thera attained arhathood on the same Nikini poya day. Nikini poya marks the commencement of "Pasu Vas" for the Bhikkhus who fail to observe the normal Vassa on the day following Esala Poya. The historical Dalada Perahera is concluded on Nikini Poya Day.